Electric contacts



May 17, 1960 w. J. WEINFURT ELECTRIC CONTACTS Filed April 18, 1957 FIG. 2.

FIGJL FIG. I.

FIG.5.

nvmvrm WILLIAM J. VIEINFURT flfd.

ATTORNEY United States Patent ELECTRIC CONTACTS William J. Weinfurt, Elm. Grove, Wis., assignor to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Application April 18, 1957, Serial No. 653,698

3 Claims. (Cl. 200-166) tact assembly having a multiplicity of separate, parallel current carrying blade elements that assure even distributron of current among several independent paths and that prohibit current from being concentrated at any of the multiple points of current interchange.

A further object of this invention is to provide a contact whose plural blade elements are independently biased into high contact pressure with a cooperating contact by means of a rubber-like plug member that deforms and develops pressure in accordance with the requirements of the individual blades.

A further object is to provide an electric contact employing a rubber-like element for jointly effecting contact pressure. and damping vibrations that are brought about when the contact is engaged. This object takes advantage of the inherent properties of rubber-like substances insofar as they do not act like efiicient springs but absorb energy when distorted and convert that energy into heat of internal friction rather than return it to the system. i

It is a general object of the invention to provide a simple and efiicient electric contact and more specific objects will appear periodically throughout the course of the ensuing specification.

A more detailed explanation of the invention will now be set forth in conjunction with the following drawing in which:

Fig. 1 is a front elevational view of the novel contact assembly shown engaged with a cooperating contact;

Fig. 2. is a side elevational view of the contact shown in Fig. 1;

Fig. 3 illustrates one of the contact blade elements isolated from the assembly shown in the preceding figures;

Fig. 4 is a fragmentary sectional view taken on the line 44 of Fig. 2; and,

Fig. 5 depicts a cylindrical, rubber-like contact pressure creating plug as it appears before it is assembled in I the novel contact.

Referring to Figs. 1 and 2, it will be seen that the contact assembly, designated generally by the reference numeral 1, comprises a base plate 2 which supports the active elements of the contact and facilitates its mounting in an electric switch by any suitable means such as terminal bolt 3, for example. 'Base plate 2 is provided with a conductive pivot shaft 4, preferably of WPPer,

2.92-7.25? Patented May 17, 1960 ice any other suitable means.

Shaft 4 carries a plurality of alternately stacked, similar, elongate blade members 5, one of which is shown isolated in Fig. 3. Blades 5 may be made of hard drawn copper or other highly conductive metal. Note in Fig. 2 that the alternate 'stacking'of'blades 5 creates spaces 6 between them which grant access to air or dielectric fluid for conducting heat away from the blades.

Eachblade is provided with a central hole 7 which closely fits over pivot shaft 4 when the blades 5 are alternately stacked. The region 8 about hole 7 is arcuate and provides a bearing surface for adjacent alternately stacked blades. On one side of hole 7 there is provided a marginal substantially semi-circular slot 9 which complements a corresponding slot in the next layer and thereby creates an approximately circular aperture when the next adjacent inverted blades 5 are stacked on shaft 4 with blade pivot holes 7 aligned on their common axes.

On the opposite side of hole 7 from notch 9 the lateral width of the blade is reduced in the region designated by the reference numeral 10. The edge 11 of the reduced portion constitutes a current interchange surface for engaging a movable contact element 12. When the blades 5 are alternately stacked as in Fig. 1, current interchange edges 11 on opposite blades are laterally spaced from each other to define a contact receiving gap 13. The extremities of the blades reduced portions are rounded, as shown, to better permit entry of contact 12 in gap 13. The minimum size of gap 13 is established by the currentinterchange edges 11 striking a fixed pin 14 which may be anchored in base plate 2 in any suitable manner.

In order to develop contact pressure between interchange edges 11 and the movable contact element 12, and to absorb the shock incident to movable contact 12 rapidly entering gap 13, there is provided a rubber-like plug member 18 which resides in the aperture that extends through the stack of blades 5' and which aperture is defined by opposite and adjacent semi-circular notches 9. Before insertion through the aperture defined by complementary notches 9, the plug has smooth external surfaces. 7

In order to assemble the alternately stacked blades 5, plug member 18 is inserted in the notch aperture and the blades are simultaneously compressed laterally so as holes 7 will align with each other so that the whole as-- sembly may be slipped onto pivot shaft 4. The stack of blades is retained on pivot shaft 4 by means of a snap ring 19 which fits into an appropriate groove immediately adjacent the outermost of the individual blades 5.

When the alternately stacked blades 5 are jointly deposited on pivot shaft 4 the blades have a tendency to rotate in parallel planes with respect to each other due to the inherent expansive force of resilient plug member 18. A certain amount of such movement is permitted but it is limited, as explained earlier, by the current interchange edges 11 striking stop pin 14. Thus, when movable contact 12 is withdrawn from gap 11, the gap is slightly smaller than the width of the movable contact.

Note in Fig. 2 that rubber-like plug 18 is allowed to extend somewhat in excess of the blade 5 stack thickness and into an appropriate hole 20 penetrating base plate 2. No other means for retaining plug 18 is necessary since the plug is tightly engaged by the shear force developed between the margin of notches 9 and the periphery of the plug.

If the surface of movable contact 12 is highly irregu- I 2,937,207 t ,v p

lar or in misalignment with the gap 11 of the novel stationary contact assembly 1, contact pressure developed between the current interchange edges 11 and the contact 12 will still be equalized because each blade is independently pivoted on shaft 4 and derives its own contact pressure from a next adjacent portion of plug member 18. It is also to be noted that with a seven blade stack constituting the contact assembly 1 as in the instant example, there are created a total of seven. independent current paths between the movable contact member 12 and the pivot shaft 4. Moreover, current is transferred directly to pivot shaft 4 through at least an equal number of independent high pressure interchange points along the interior margins of pivot hole 9 in each blade. Hence, not only are the current paths subdivided but they are widely dispersed so as to avoid concentration of current, and incidentally heat, at any particular region of the assembly 1.

When movable contact 12 is withdrawn from gap 13, 1

the gap is diminished by a rotary force on the blades exerted by plug member 18. When movable contact member 12 is again plunged into gap 13-, angular acceleration is imparted to each blade 5 and there is a tendency for vibration of the blades to occur. However, in the instant invention, advantage is taken of the inherent property of rubber-like materials to the extent that they absorb more energy than they return to a vibrating system. Thus, when the blades 51 are impacted by reception of movable contact 12, the energy of impact is absorbed by the deformation of plug member 13 and there remains stored in the plug member some residual force for developing contact pressure between blades 5, the movable contact member 12 and the pivot shaft 4.

It will be appreciated that the number of current paths and current interchange points in the novel contact assembly can be varied according to the current carrying capacity required in a particular piece of apparatus by merely increasing the number of blades 5 in the stack and, of course, making appropriate adjustments in the length of the rubber-like plug 6, pivot shaft 4, and stop pin 14.

Although a preferred form of the invention has been illustrated and described, it will be understood that such disclosure is to be construed as exemplary rather than limiting, for the invention may be variously embodied and is to be interpreted according to the claims which follow.

It is claimed:

1. A switch contact assembly comprising a plurality of alternately stacked elongate blades each of which has an intermediate hole, a laterally reduced margin on one side of the hole and a notch on the other side thereof, a conductive shaft upon which said blades pivot and upon which they are stacked in complementary relation with respect to each other to define a contact receiving gap between reduced margins and an aperture defined by complementing notches, stop means disposed in the contact gap for limiting rotation of alternate stacks toward each other, and a rubber-like plug member projecting through said aperture and being in compressive shear by said alternate blades, whereby said plug member urges said alternate stacks of blades toward rotation against said stop means.

2-. A switch contact assembly comprising at least a pair of blade means, a conductive pivot shaft means on which said blade means are journalled intermediate their opposite respective ends, contact tip means near an end of each blade means on one common side of the shaft means disposed in opposite complementary relation with respect to the contact tip means of the other, an elastic body of rubber-like material disposed compressively between said blade means on the other side of the shaft means in relation to the contact tip means, said elastic body tending to expand outwardly to thereby urge said blade means toward rotation in opposite directions about the pivot shaft.

3. A switch contact comprising at least a pair of blade means adjacent each other and pivoted intermediate their opposite respective ends, each blade having contact tip means on one common side of the pivot disposed in opposite complementary relation with respect to the contact tip means of the other for defining a movable contact receiving gap therebetween, an elastic body of rubber-like material interposed between said blades on the other common side of the pivot remote from said gap, said elastic body being in compressive shear between said blades and tending to expand outwardly and thereby urge said blades toward rotation in opposite directions about the pivot and toward closing said gap, and stop means disposed in said gap for receiving the force of said blades when said gap is unoccupied.

References Cited in the file of this patent UNITED STATES PATENTS 

